Helically crimped vinyl filament



April 7, 197 0 .1. J. ME ERS' ET AL HELICALLY CRIMPED VINYL FILAMENT Filed June 22, 1967 United States Patent M 3,505,163 HELICALLY CRIMPED VINYL FILAMENT Jacques J. Meers and Frederic C. Merriam, Danvers, Mass., assignors to USM Corporation, Flemington, N.J., a corporation of New Jersey Filed June 22, 1967, Ser. No. 648,150 Int. Cl. D02g 3/44, 1/02; A46b /00 US. Cl. 161-173 2 Claims ABSTRACT OF THE DISCLOSURE The present invention is directed to producing helically crimped filaments and particularly filaments of essentially rigid vinyl material adapted for use as load bearing bristles.

Load bearing bristles of essentially rigid vinyl material are used in producing stiff brushes or brush surfaces such as those used in abrading and cleaning as well as other production operations. In addition they have other uses, among them in various mats designed to provide treading, driving, skiing and other heavy wearing surfaces.

In providing filaments of essentially rigid vinyl material in condition for use as bristles, it is common practice to provide them with a crimp. Products such as brushes, brush surfaces, mats, etc. using crimped filaments as bristles show improved body and load bearing characteristics. This may be noted by comparing them with products having the same bristle density, that is, number of bristles in a unit area, but using straight filaments or bristles.

As presently practiced filaments of essentially rigid vinyl material designed for use as crimped bristles are provided with a fiat crimp. This practice prevails despite the fact that potentially filaments provided with a helical crimp are more desirable, requiring even less bristle density to produce products having the same body or load bearing characteristics. The reason for this apparently unlikely choice is that attempts to produce helically crimped bristles have resulted in stressed products which evidence a higher incidence of fracture than do fiat crimped filaments of the same vinyl material, when both are subjected to work loads.

It is an object of this invention to produce helically crimped filaments of essentially rigid vinyl material which are adapted for use as load bearing bristles.

It is another object of this invention to produce helically crimped filaments of essentially rigid vinyl material which are nonstressed products.

It is another object of this invention to produce helically crimped filaments of essentially rigid vinyl material which do not evidence a higher incidence of fracture than do flat crimped filaments of the same material when subjected to work loads.

These and other objects of this invention are obtained in a process which comprises the steps of (a) stretching between about 150% and 600% filaments of essentially rigid vinyl material while the filaments are in heat soft- 3,505,163 Patented Apr. 7, 1970 ened condition, (b) cooling the filaments to solidified condition and while maintaining them in the stretched condition intertwisting a plurality of them together, then (c) heating the stretched, intertwisted filaments to impress them in the intertwisted form, and (d) while maintaining the filaments in intertwisted, stretched condition cooling the same to solidified condition.

The folowing drawings are included for the purpose of illustrating the invention, in which:

FIG. 1 is a schematic view of apparatus which may be used in helically crimping filaments of essentially rigid vinyl materials;

FIG. 2 is a perspective view, with parts broken of two of the filaments twisted together; and

FIG. 3 is a perspective view, with parts broken of the filaments, separated and provided with a helical crimp.

The essentially rigid vinyl materials, from which the filaments used in practicing the present invention may be formed are polyvinyl chlorides and polyvinyl dichlorides. In addition to the vinyl chloride or vinyl dichloride monomer, those polymers may include minor portions of another monomer or monomers such as vinyl acetate, which is present in less than about 15 percent by weight. Thus the vinyl materials or polymers may be homopolymers or copolymers with, however, the preference lying with homopolymers. In addition to that the vinyl materials may also contain small amounts of other synthetic polymeric materials, blended with them. As an example of that polyvinyl acetate may be used. It is preferred that the amount of the other synthetic polymeric material be less than about 15 percent by weight of total material.

The vinyl materials for use are termed essentially rigid to indicate that semirigid vinyl materials are also intended. This further indicates that the vinyl materials for use are essentially unplasticized in nature, or that they contain less than 15 percent by weight of a plasticizer. Plasticizers are included primarily to improve the processability of material, and 'so may be also considered lubricants, processing aids, etc. Many of the common plasticizers operate to provide this function or functions. These include such common plasticizers, or compounds commonly referred to as plasticizers, more specifically external plasticizers such as dibutyl sebacate, dioctyl phthalate, etc. as well as the internal plasticizers which are included as monomeric components in the original polymerization of the polyvinyl chloride. This letter has reference to the copolymers mentioned previously. To return then, when stabilizers and other adducts are used again to improve processability or as protection for the material in final product form, and this is usual practice, they too may have plasticizing characteristics. An example of the preceding is dibutyl tin dilaurate stabilizer. In that event the stabilizer, etc. is considered as being a plasticizer and included in the total amount calculated as plasticizer.

The polymers constituting the vinyl materials used in practicing this invention are those which are preferably medium and high molecular weight. This is reflected by polymers having intrinsic viscosities of greater than about 0.70 as determined by ASTM D124360.

The filaments used as starting materials in practicing this invention may be provided by or from practice of a number of known extruding techniques. Filaments which are used in producing load bearing bristles generally have diameters ranging from about 0.15 millimeter to about 6.50 millimeters and more commonly 0.20 millimeter to about 1.50 millimeters. To return, one such extruding technique is that in which the vinyl material in pellet or other comminuted form, is directed into an extruder provided with a spinerette type head capable of delivering monofilaments. In the extruder the vinyl material is converted to a fluid melt, and then drawn out through the head as a plurality of continuous, extended filaments or monofilarnents. This initial drawing is usually 125% to 200% of original extruded length. The filaments may then be cooled and if desired cut into desired lengths.

In practicing this invention, drawn filaments are heated to a temperature at which they become soft, or heat softened. This is a temperature well below the melting point for the vinyl material from which the filaments are constituted. In the case of rigid homopolymers of polyvinyl chloride, a temperature, for example, ranging between about 90 C. and about 110 C. may be used. In the usual case about 100 C., which is conveniently obtainable in a water bath, oven, etc., is used. In heat softened condition, the filaments are stretched between about 150% and 600% of their drawn or initial drawn length, that is, the length obtaining after drawing from the extruder or other filament producing means. A more preferred stretching length is about 300% and 400% based on drawn length. Stretching may be effected in a single stretching step, or in a number or series of stretching steps.

After being stretched, the filaments are maintained under tension or in the stretched condition and cooled or allowed to cool to a temperature below the softening temperature. In that condition, that is, the cooled and stretched condition, or, while maintaining the filaments under tension, a plurality, two or more, of the filaments are intertwisted. In the usual practice two filaments are intertwisted together. Intertwisting provides each or both filaments in or with a helical shape. That shape may be varied as to period or frequency by the tightness of the twist introduced, the relative thicknesses or diameters, one to the other, of the filaments being intertwisted, the number of filaments inter-twisted together, etc. It is pre ferred practice to intertwist two filaments of equal diameter together, and in doing so arrive at a crimp period of one complete crimp or turn in about 3 to about 20 filament diameters of filament length. A more preferred range is a complete crimp or turn in about 7 to 12 diameter lengths. By providing the filaments with a uniform twist the helical crimping finally obtained is uniform, and, so are the physical properties over the length of the filaments. The amplitude of the twist and eventually the helical crimp, may be varied principally by varying the relative thicknesses or diameters of the filaments practiced on in the intertwisting step or operation. With filaments of the same diameter a preferred helical crimp amplitude range is from about 2 to times the diameter of the filament to give bristles of good body for use in brushes, mats, etc.

After the filaments are intertwisted they are maintained as such and heated to provide them at a temperature above their softening temperature, again about 90 C. to 110 C. They are maintained at this temperature for a period suflicient to impress or introduce the twist form, which is helical in shape into the filaments. This may be accomplished in a short period, on the order of less than about 5 seconds generally being sulficient to accomplish impressing.

After being impressed into twisted or helical shape, the filaments are allowed to cool or are cooled to a temperature below the heat softening temperature. That serves to set the impressed helical shape or crimp in the filaments. Simply allowing the temperature to drop to room temperature works well in this regard. The intertwisted filaments may be kept in cooled condition for an extended period if desired, however, it is not necessary to do so. The intertwisted filaments in which the helical crimp is then set, may be separated or disengaged one from the other. On doing so they retain the helical shape or crimp introduced into them by the impressing operation. Thereafter, too, the helically crimped filaments may be chopped or otherwise cut or subdivided into bristle lengths. This last operation may also be carried out prior to separating or disengaging the filaments one from the other. Either way the filaments retain the helical crimp introduced to them by impressing them while in intertwisting form.

Reference is now made to the drawings. For convenience in describing the invention, the apparatus of FIG. 1 is shown adapted to process two filaments of essentially rigid polyvinyl chloride and in doing so includes filament extrusion and separation operations. The results obtained from such an adaptation are reflected in the products shown in FIGS. 2 and 3.

The apparatus of FIG. 1 is provided at its starting point with a screw type extruder 10 located on a stand 12. Extruder 10 includes a charging hopper 14 and a multiple filament die head 16 located on extruder barrel 18. Rigid polyvinyl chloride starting material, in pellet or other convenient starting or charging form may be charged into hopper 14. From the hopper 14 the material is routed into the barrel 18 and is there worked into melt form. The melt is then extruded out of the die head 16 in the form of a pair of continuous filaments or monofilaments 20 and 22.

After being extruded, the filaments 20 and 22 are passed into a cooling bath 24 held in a tank 26. To insure immersion of the filaments 20 and 22 within the cooling bath 24 they travel under a guide roll 28 located at the bottom of the bath. A pair of attached bearing brackets 30 and 32 are used to attach the roll 28 to the bottom, not shown, of tank 26. The cooling bath may be water or other liquid which is nonreactive with polyvinyl chloride. The bath is usually maintained at a temperature somewhat above room temperature, on the order of 40 C. to 60 C. operates well in this regard.

From bath 24, the filaments 20 and 22 are directed in S-wrap fashion through a pair of metering rolls 34 and 36. In addition to metering the thicknesses of the filaments 20 and 22, the rolls 34 and 36 perform additional functions. They serve to draw the filaments 20 and 22 from the die head 16 and through the cooling bath 24. In doing so they are generally set to draw the filaments 20 and 22 to about 125% to 200% of their extruded length. They also serve as snubbing rolls for the stretching step which follows.

The filaments 20 and 22 are directed from the rolls 34 and 36 into a stretching oven 38 enclosing an atmosphere heated to about C. This temperature is above the heat softening temperature for rigid polyvinyl chloride. While in the oven 38, the filaments 20 and 22 are stretched about 350%. To facilitate stretching, a pair of stretch rolls 40 and 42 are operated at a speed comparably faster than the speed at which the rolls 34 and 36 operate. Filaments 20 and 22 are directed through the rolls 40 and 42 in S-wrap fashion, and, from there are routed into a cooler 44. In the latter, the atmosphere is maintained at about 5 C. to 15 C. The lengths of the filament 20 and 22 are maintained constant as they pass through the cooler 44. To facilitate that, the rolls 46 and 48 are operated at the same speed as are the rolls 40 and 42. The filaments 20 and 22 are passed through the rolls 46 and 48 in S-wrap fashion.

After passing through the rolls 46 and 48 the filaments 20 and 22 are taken up on winding spools 50 and 52 located on a winding stand 54. The filaments 20 and 22 are wound onto the spools 50 and 52 under tension in order that they be maintained in the stretched condition. Each of the spools 50 and 52 are shown provided with winding guides 56 and 58.

With or during winding of the filaments 20 and 22 onto the spools 50 and 52, the filaments 20 and 22 are maintained under room temperature.

The spools 50 and 52 are transferred from the stand 54 to an intertwister constituting a variable speed electric motor 60 provided with a spinner plate 62 mounted on a motor shaft 64. For convenience of expression the transferred spools are designated 50:: and 52a respectively, and, as shown, they are stationed on a pair of bracket members 66 and 68 attached to the spinner plate 62. Actuation of the electric motor 60 causes rotation of the spinner plate 62 carrying spools 50a and 52a. Intertwisting of the filaments 20 and 22 is caused by rotation of the spools together with unwinding of the filaments 20 and 22 off the spools. The filaments 20 and 22 are guided by a ring 70 into rolls 72 and 74 from which they pass through in S-wrap fashion. Drag mechanisms, not shown, serve to insure that the filaments 20 and 22 are maintained in the stretch or tensioned condition as they are wound old? the spools 50a and 52a and intertwisted or twisted together. The intertwisted filaments 20 and 22 take the helical shape shown in FIG. 2.

From the rolls 72 and 74 the intertwisted filaments 20 and 22 are directed into an oven 76 enclosing an atmosphere heated to about 100 C. In the oven 76 the twist, or helical shape, introduced earlier by intertwisting becomes impressed into the then heat softened, and stretched intertwisted filaments 20 and 22. The stretched, intertwisted filaments 20 and 22 are directed through the oven 76 under tension. To effect this, the rolls 78 and 80 are operated at slightly faster speed than are the rolls 72 and 74. On leaving the oven 76 the stretched intertwisted filaments 20 and 22 are maintainedin that condition and allowed to cool. This effects setting of the helical shape or crimp impressed into them in the oven 76. Specifically then, on leaving the oven 76, the intertwisted filaments 20 and 22 pass through the rolls 78 and 80 in S-wrap fashion and on leaving them are wound up, under tension, onto a spool 82. That latter includes a winding guide 84 and is located on a winding stand 86. During windup the intertwisted filaments 20 and 22 are maintained under tension and are allowed to continue to cool at a temperature below their heat softening temperature.

At this point in the operation, the intertwisted filaments 20 and 22 have had introduced into them a permanent helical crimp, and, they can be cut to length and used as bristle stock in their intertwisted form, that is, the form shown in FIG. 2. Alternatively they may he sepa rated or disengaged from one another while in extended form. Either way a permanently, helically crimped prod uct such as that shown in FIG. 3 may be obtained.

The apparatus shown in FIG. 1 is designed to separate the intertwisted, helically crimped filaments 20 and 22, while they are in extended form. Using the apparatus shown there in simplified form to do so, the spool 82 holding the intertwisted helically crimped filaments 20 and 22 is transferred to a separation stage, and, specifically onto a stand 88. In order to avoid confusion the spool 82 is then designated 82a. The filaments 20 and 22 are unwound from the spool 82a directed through a ring 90 and are separated as they are advanced separately through individual holes, not shown, in a stop plate 92 forming the front portion of a cage 93. The crimped filaments 20 and 22 are taken up individually onto spools 94 and 96 which are provided with winding guides 100 and 102 respectively. In order to facilitate winding onto the spools 94 and 96, the spools together with the cage 93, which includes a base plate 98 are designed to be rotated all relative to one another. In actual practire gearing is used which is designed to prevent introduction of cold twist into the filaments 20 and 22 as they are being separated. The apparatus may include an electric motor 104 having a shaft 106 attached to the cage base 98. The shaft 106 clears through a gear 108 which is maintained stationary relative to the electric motor 104. With rotation of the shaft 106 gears 110 and 112 attached to shafts 114 and 116 are rotated and in turn cause rotation of spools 94 and 96. With actuation of motor 104 rotation of cage 93 and spools 94 and 96 is effected and the filaments 20 and 22 are wound up separately onto the spools 94 and 96. At this point filaments 20 and 22 each provided with a permanent helical crimp, may be taken ofi spools 94 and 96 and cut into the desired bristle length, as their particular end application or applications dictate.

The following example is provided for the purpose of further illustrating the invention.

EXAMPLE 1 A stabilized, unplasticized polyvinyl chloride material having an intrinsic viscosity of 0.84 is charged, in powder form, into a 1.5 inch extruder (Hartig 15T20). The extruder is provided with a pair of 2.0 millimeter streamlined dies. A melt temperature of 195 C. is used and the extruder is set to deliver 90 grams per minute at 16 r.p.m.

A pair of monofilaments are taken off the die, directed through a water bath having a temperature ranging C.55 C., and through a pair of metering rolls. The filaments obtained at that point are 1.5 millimeters in thickness and drawn ISO-170% of their extruded length.

The filaments are then directed into an oven set at 100 C. where they are stretched 340% of their drawn length. After stretching the filaments have diameters of 0.8 millimeter. They are wound up on separate spools under tension, and allowed to cool to room temperature.

The spools carrying the stretched filaments are set up in an intertwisting device. Tension on the strands, as they are taken off the spools is maintained through the use of friction brakes. Intertwisting is carried out at room temperature. The spinning disc is spun at 400 rpm, and

' the filaments are advanced through intertwisting at 4.0

meters per minute.

The filaments, in intertwisted form, or as an intertwisted assembly are directed under tension into an impressing oven, set at C. and having a 0.5 meter oven length. The intertwisted filament assembly is advanced through the oven at 4.0 meters per minute. A set of rolls are operated to advance the assembly at the indicated speed of advance.

The intertwisted and now helically crimped filament assembly is cut to 76 centimeter lengths as it advances beyond the rolls. The individual filaments in the assembly are then separated one from the other, and cut or chopped into 8.3 centimeter bristle lengths. Each of the bristles so obtained has a helical crimp with a frequency of one turn per centimeter of length and an amplitude of 1.6 millimeters from outside to outside.

The bristle lengths obtained above are used to produce open circular wire brushes having metal ferrules. Brushes of similar construction and bristle density are made from bristles which have flat crimp but which are otherwise similar to the bristles here provided with helical crimp, It may be noted that the brushes made up from the helically crimped bristles are fuller or have more body than the brushes made up from the flat crimped bristles. When the brushes are subjected to similar abrading situations to wit: using simulated ski bottoms, it is noted that the brushes containing the helically crimped bristles or filaments exhibit better load bearing properties with less breaking off of the bristles taking place.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above process and in the bristles or filaments set forth without departing from the scope of the invention, it is intended that all matter contained in the description and shown in the accompanying drawings may be interpreted as illustrative and not in a limiting sense.

Having thus described our invention What we claim as new and desire to secure by Letters Patent of the United States is:

1. A helically crimped filament adapted for use as a load bearing bristle consisting of essentially rigid vinyl 5 material, the filament having a diameter ranging from 0.15 millimeter to about 6.50 millimeters and a crimp period of one complete crimp in about 3 to about 20 filament diameters of length.

2. A helically crimped filament according to claim 1 10 wherein the filament has a diameter ranglng from about 0.20 millimeter to about 1.50 millimeters.

References Cited UNITED STATES PATENTS 8/1958 Peterson 15159 3/1966 Charvat 15-l59 ROBERT F. BURNETT, Primary Examiner LINDA M. CARLIN, Assistant Examiner Us. 01. X.R. 15 1s9 

